Core constructions



API 30, 1957 B. A. WYMAN 2,790.960

CORE CONSTRUCTIONS 4 INVENTOR Burton A. Wymon MMX/@m 6 ATTORNEY April 30, l957 B. A. wYMAN 2,790,960

CORE CONSTRUCTIONS Filed Jan. 5l, 1952 3 Sheets-Sheet 2 Burton A. Wyman www" M ATTORNEY April 30, 1957 Q/L ib Burton A. Wyman BY @mim ATTORNEY United States Patent() CORE coNsTRUcTloNs Burton A. Wyman, Cleveland, Ohio, assignor to Westinghouse Electric Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania Application January 31, 1952, Serial No. 269,27 7

8 Claims. (Cl. 336-165) This invention relates generally to core constructions, and more particularly to multiple coil `core constructions such as are employed for the transformer and ballast coils used for the control of a plurality of fluorescent lamps.

Core constructions of the multiple coil type, having a number of separate openings for different coils, and providing different reluctance paths for flux of the ditlferent coils and consequently dierent values of reactance for the coils, have been variously constructed in the past in laminated form, `with each lamination being formed of one or more pieces to constitute winding and yoke sections, with certain gaps in the magnetic circuit to provide high rea-stance magnetic leakage paths. Since the laminat-ions are usually stamped out of sheets of magnetic material, variations in dimensions roccur in 'assembly which cause undesirable variations in coil reactances which may result in improper :lamp operation.

Accordingly, one object of this invention is to prov-ide a novel core construction fof the type described made 'of relatively few parts which are .readily adjustable during assembly to compensate for manufacturing variations.

Another object of this invention Iis .to provide a novel form of core lamination, for a core of the type described, all parts t` which may be accurately :stamped out ol` a sheet of material in one stamping operation.

Another object of this invention is to provide .a core of the type described having two gaps in the magnetic circuit, wherein the laminations are so formed and arranged as to `permit adjustment tor" one or both gaps.

Still another object of this invention is to provide a novel core construction of relatively few .parts which may be stamped out or a sheet of material with a mini mum of Waste.

These and other objects of this invention will become more .apparent upon consideration of the following dctailed description of preferred embodiments thereof, when takeninconnection with the attacl-iedfdrawings, in which:

Figure l is a plan view of .a core lamination as it appears immediately after it is stamped out lof ka sheet of magnetic material;

vFig. 2 is a plan view of `an .assembled core made up of thelaminations shown inFig. 1';

Fig. 3 is a plan view of a lamination employed in thel core structure shown in Fig. as -it appears immediately after it is stamped out of la sheet of magnetic material;

Fig. 4 is an end view o'f a core constructed in accordance with this invention, with this View being representative of all the forms of core structures .herein disclosed, but being specifically a view of the right-hand end ot the core structure shown in Fig. 2;

Fig. 5 isa plan view of a. modified form of core construction;

Fig. 6 is a plan view ot' a lamination similar to that shown` in Fig. 1 but Villustrating a slight modification `in form and appearance thereof immediately following the stamping operation;

ICC

Fig. V7 is a plan View of still another modified core construct-ion;

Fig. 8 is a schematic view of the coils which are adapted to be mounted in the core structures disclosed herein, and illustrates the manner in which these coils are connected;

Fig. 9 is a plan view of a lamination similar to those shown in Figs. 1 and 6, Ibut illustrating a different arrangement of the core parts immediately following the stamping operation;

Fig. l() is a plan view of a modified form of core structure, and

Fig. l1 is a plan view of the core structure shown in Fig. l() but with the parts assembled in a different relation.

The core structures constructed in accordance with this invention, examples of which are specically hereinafter described, are all adapted to be built up of a plurality of laminations, with each lamination comprising only two parts which may be stamped out of a single sheet ot' magnetic material. This is achieved in accordance with this invention by stamping out the two parts of the core in such relation that very close control is maintained of the parts which form magnetic leakage gaps in the assembled core structure, while retaining provision for some adjustment of both such gaps.

The core structure 2 shown in Fig. 2 of the drawings is built up of a plurality of laminations, each of which comprises two parts. One part of each lamination is a generally U-shaped yoke 4 having a bight portion n connecting identically formed legs 8 which are of substantially E shape. Each leg 8 of the yoke 4 has opposed, laterally inwardly extending projections 1G at the outer ends thereof, and intermediate opposed, laterally inwardly extending projections 12 and 14, with the arrangement being such that the projections 10, i2 and 14 extend inwardly towardseach other, respectively.

The other part of each lamination comprises a winding leg 16, which is simply a rectangular-shaped strip of magnetic material having opposed recesses 18 at one intermediate point in opposite side edges thereof. Coils may be readily slipped onto this type of winding leg, and when the two parts of each ylamination are assembled in the manner shown in Fig. 2, the recesses 18 in opposite sides of the winding leg 16 lie opposite the projections 12 of the yoke 6, to form therewith leakage gaps 22.

The two parts of each lamination are also assembled so4 that there is a gap 20 between the inner end of the winding leg 16 and the bight portion 6 of the yoke.

lt will be observed that the recesses 18 are of greater length than the width of yoke projections 12, so that gap 20 may be adjusted within predetermined limits without affecting leakage vgaps 2-2.

A marked advantage of this construction is that the two parts of each lamination may be stamped out of a sheet of magnetic material in one operation with the parts arranged as shown in Fig. l, where the recesses 18 in the winding leg 16 are positioned in the space between yoke projections 12 and 14, so that very close control ot' the dimensions of these recesses may be readily -maintained. After the parts of each lamination are thus Ystamped out, the core may be very easily assembled merely by turning the winding 4leg 16 end-for-end to position its recesses 18 opposite yoke projections 12, respectively.

The particular forni of core structure shown in Fig. 2

as well as those to behereinafter described, are especia-lily adapted for use with the coil arrangements, particularly described and claimed in the copending application of W. Oglesbee and A. R. Cornell, Serial No. 267,627, filed January 22, 1952, on Apparatus for Operating Gaseous Discharge Devices, and assigned to the same .assignee Vof` this invention. Accordingly, for a. complete :description of such apparatus, reference is hereby made to the above copending application.

When the core is assembled as shown in Fig. 2, the two parts of each lamination may be secured together in any desired manner, such, for example, as by bolts and clamping brackets, or by suitable Welds 23 and 25. By referring to Fig. 8 of the drawings, the general arrangement ot' coils adapted to be employed with the core structure 2 and the other core structures to be hereinafter described is seen to comprise an auto-transformer coil 24 which is adapted to be placed in the central winding space between yoke legs 12 and 14 of the core structure. The auto-transformer coil 24 has a primary portion 26 and a secondary portion 28, with the primary part 26 thereof adapted to be connected to a source ot low voltage electric energy by supply conductors 30 and 32. The coil arrangement illustrated is intended Yfor the open ation of a pair of gaseous discharge devices, such as uorescent lamps, and for this purpose there is provided a lead coil 34 connected to the secondary part of the auto-transiormcr coil 24 and having a conductor 36 which in Series with a capacitor, leads to one terminal ot a gaseous discharge device, the other terminal of which is adapted to be connected to the supply conductor 30. The lead coil 34 is adapted for mounting in the winding space between yoke legs 14 and the bight portion 6 of the yoke, and it is termed a lead coil because of the capacitor incorporated in conductor 36 to provide a leading current for the lamp to which it is connected. The other gaseous discharge device is adapted to be connected between the supply conductor 3G and a conductor 4i? having lag coil 33 in series therewith connected to a tap on the autotransformer coil which may be, as is illustrated, at the junction of the primary and secondary portions thereof. The lag coil 38 is adapted to bc mounted in the remaining mounting space of core structure 2, namely, the space between yoke projections and 12.

It will be apparent that with coils 28, 34 and 38 mounted in the yoke structure 2 in the manner described above and connected to a pair of iluorescent lamps in the manner pointed out, the lamp which is connected across conductors 30 and 36 has a high voltage applied thereto which comprises the sum of the source voltage across supply conductors 30, 32 and the voltage induced in the secondary portion 28 of the auto-transformer coil.

This is the open circuit voltage which is above line voltage in order to start the lamp.

There is little or no voltage induced in lead coil 34, because of the high reluctance of air gap in the magnetic circuit of the core structure, which effectively substantially isolates the lead coil 34 from the magnetic effects of the auto-transformer coil, although both coils have a portion of their magnetic circuits through the structure in common, namely, the yoke projections 14.

After the lamp starts, the coil 34 has a reactance determined largely by the air gap 20.

The other lamp which is connected across conductors and 40 also has a high voltage applied thereto com prising the sum of the supply voltage across conductors 30, 32 and the voltage induced in lag coil 38. It will be observed that lag coil 38 is in the same magnetic circuit with the auto-transformer coil comprising the portions of the winding leg 16 and yoke legs 8 between yoke projections 10 and 14, and including the projections 10 and 14, to thus induce a voltage in the lag coil 38.

When the lamp starts, coil 38 acts as a reactor having air gaps 22. The lamp then is ballasted by the reactance of this coil.

It will be appreciated that in order to maintain close control of the reactances of lag coil 38 and lead coil 34, the dimensions of gaps 20 and 22 must be closely regulated, and that the core construction shown in Fig. 2 lends itself to such close control of gaps 22 while being easy to assemble, and providing ready adjustment for the remaining gap 20.

Each lamination Aof the core structure 2 of Fig. l may be stamped out in one operation with the two parts of each lamination arranged as shown in Fig. 6 of the drawing, instead of the arrangement shown in Fig. l. The reason why the winding leg 16 extends at its outer end beyond yoke projections 10, is that for certain dimensions between yoke projections 10, 12 and 14 and the bight portion 6 thereof, the punching operation cannot be accomplished with the winding leg at the position shown in Fig. l of the drawings. ln such a case the punching may be effected with the parts in the relative positions shown in Fig. 6, and the laminations then assembled by merely turning the winding leg 16 endfor-end to the position thereof shown in Fig. 2. Alternatively, it may be necessary to punch. the parts ol' the lamination out at the relative positions shown in Fig. 9 ot the drawings, an assembly effected very simply by merely pushing winding leg 16 inwardly until recesses 18 appear opposite yoke projections 12, and the proper gap 2f) is obtained at the inner end of the winding leg. While yokes stamped out with the parts positioned as shown in Figs. 6 and 9 will result in more waste material than a stamping operation performed with the parts positioned as shown in Fig. l, it will be observed that all the advantages oi the previously described core structures are retained in that the gap recesses may be accurately corr trolled, and assembly of the laminations is effected in an extremely simple manner.

The core construction 42 shown in Fig. 5 is similar to that shown in Fig. 2, in that it has laminations, each of which is composed of two parts, with one being a U shaped yoke 44 having identically shaped legs 46, and a connecting bight portion 48. The legs 46 of the yoke 44 have opposed, spaced, inwardly extending projections 50, 52 and 54 located at positions corresponding to the legs 10, 12 and 14 of the yoke 4 shown in Fig. 2, butin stead of having these projections of equal length as is the case in Fig. 2, only projections 50 and 54 are equal in length, and the intermediate projections 52 are shorter. The winding leg 56 in this embodiment of the invention is simply a rectangular strip of magnetic material having projections 58, adapted, when the core is assembled, as shown in Fig. 5, to be positioned in the space between projections 52 and 54 to form magnetic leakage gaps 62 -f between projections 52 and winding leg 56.

It can thus be seen that when the core is assembled with the laminations secured by welding, for example, at the points 64 and 66, that the core structure 42 provides a magnetic circuit similar to the core structure 2 previously described, in that it has the leakage gaps 62 located between the space for the auto-transformer coil (between yoke legs 52 and 54) and the space for the lag coil (the space between legs 50 and 52), and a variable gap 60 is also provided in the magnetic circuit for the lead coil (positioned in the space between bight portion 48 of the yoke and the yoke projections 54).

The core structure 42 may also be stamped out of a sheet of magnetic material, wtih the two parts of each lamination arranged as shown in Fig. 3, namely, with the winding leg 56 being turned in end-for-end relation relative to its position in the assembled core shown in Fig. 5. The core structure 42 thus has the same advantages pointed out above for the core 2, in that very close control of the projections 52 may be maintained in stamping these parts out, inasmuch as they are definitely located relative to each other during the stamping operation, and assembly is readily effected merely by turning the winding leg 56 end-for-end to the position shown in Fig. 3. Also the gap 60 may be readily adjusted during assembly by longitudinal movement of the winding leg 56 relative to the yoke 44 without disturbing gaps 62.

The core 63 shown in Fig. 7 has a generally Ushaped yoke 65 for receiving a winding leg 76. The yoke 65 has a bight portion 78 and legs 80, with the latter having laterally extending opposed projections 82 at the outer ends thereof, and similarly extending opposed projections S4 at an intermediate point. The winding leg `76 is provided with shallow recesses 86 in opposite sides thereof adapted to form leakage gaps with yoke projections 84, and has inwardly spaced therefrom opposed projections 88. When the core 63 is assembled as shown in Fig. 7, engagement of yoke projections 82 with the winding and engagement of winding leg projections 88 with the yoke legs 80, tix the spacing of the gaps between yoke projections 84 and the winding leg. As in the previously described cores, adjustment of the ygap between the inner end of the winding` leg and the bight portion 'it of the yoke may be readily effected during assembly by longitudinal movement of the winding leg 76, and the parts then secured as by welding at 68 and 69.

Core 63 may also be punched out of a sheet of magnetic material in a single punching operation, preferably with the winding legs arranged in end-for-end relation with respect to the position shown in Fig. 7. An advantage of this construction is that in assembling the coils which occupy positions at opposite sides o'f the winding leg projections 88, the tubes on which they are wound are positively prevented from being jammed too close to each other, as might occur with the other core constructions herein described and illustrated, as yfor example with the I core 2 shown in Fig. 2, the coil tubes might be jammed between yoke projections 14 and the Winding leg r16, and

thus increase the reluctance of the primary ilux path.

The core structure 67 shown in Fig. l0 of the drawings also employs a yoke which is identical to that em- .f.

of the leakage gap located between the auto-transformer and lag coils. This is achieved by forming the winding leg 70 with stepped recesses at opposite sides thereof, comprising a relatively deep step 72, andan adjoining relatively shallow step 74. Each lamination of the core structure 67 is preferably stamped in one operation with the parts located at the relative positions shown in Fig. l of the drawings for maintaining the greatest accuracy of gap dimension. The core structure v67 may then be assembled with the parts in the relative positions in which they are stamped out, namely, the Vpositions shown in Fig. l0, or if smaller gaps between the winding leg 70 and core projections 12 are desired, 'the Winding leg may simply be turned end-for-cnd to the position shown in Fig. 1l to bring the shallow step 74 thereof in opposition to yoke projections 12. Moreover, these air gaps may be varied by a number of steps corresponding to the number of laminations in the core structure, from the maximum gap dimension shown in Fig. l0 to the minimum gap dimension in Fig. ll, by reversing only a part of the Winding legs 78 in the stack of laminations to thus obtain a corresponding adjustment of the reactance of the lag coil, which is mounted in the coil opening between yoke projections and 12. Since both the steps 72 and 74 are of greater length than the width of yoke projections 12, the gap between the inner end of winding leg 70 and the bight portion 6 of the yoke 4 may also be readily adjusted, with the adjustments for both sets of gaps being independent of each other.

lt can thus be seen that in all of the core constructions herein described as well as other variations of this invention which might be made, the core constructions are made up of a number of two piece laminations constructed in a novel manner to permit each lamination to be stamped out of a single sheet of magnetic material, while maintaining maximum control of air gap dimensions, and permitting independent adjustment of at least one gap during assembly of the core structure, and in the case of the embodiment shown in Figs. 10 and l1, adjustment may be made of all air gaps independent of each other.

Having described preferred embodiments of the inverttion in accordance with the patent statutes, it is desired that the invention be not limited to these partcula-r constructions because it will be obvious to persons skilled in the art that the invention may take other specific forms lwithin the broad spirit and scope thereof. Accordingly, it is desired that the invention be interpreted as broadly as possible, and that it be limited only as required by the prior art.

I claim as my invention:

l. A core construction comprising, an elongated winding leg, a yoke member at one side of said winding leg an-d having a plurality of spaced lateral projections thereon of equal length extending toward said winding leg, two of said projections engaging the adjacent side of said Winding leg, a gap between a third of Isaid projections and the adjacent side of said winding Ileg for-med by a recess in said adjacent side located opposite said third projection at one position -of said winding leg where it is substantially coextensive with said yoke member, yand when said winding leg is turned end-orend `and again positioned to be substantially coexltensive with said yoke member said recess twill be offset from all 4oi said projections and all of said projections will engage the adjacent side of said winding leg.

2. A core construction comprising, an elongated winding leg, a yoke member at `one side of said winding leg and having a plurali-ty of lateral projections thereon extending toward .said winding leg, two of said projections engaging the adjacent side of .sa-id winding leg, a gap between a third of said projections and the adjacent side of said winding leg formed by a recess in said adjacent side located opposite said third projection at one position of said winding leg where it is substantially coex-tensive with said yoke member, and when .said winding leg is turned end-for-end and again positioned to be substantially coextensive with said yoke member said recess will be offset from all of said projections, said yoke member having a fourth lateral projection at one end Iwhich extends across the adjacent end of said winding leg but is spaced therefrom to form another gap, .and said recess being of greater extent than the width of said third projection so that the length of said other gap may be adjusted by longitudinal movement of said winding leg Without aiecting the first-mentioned gap.

3. A core construction comprising, an elongated winding leg, a yoke member at one side of said Winding leg and having a plurality of lateral projections thereon extending toward said Winding leg, two of said projections engaging the adjacent side of said winding leg, a gap between a third lof said projections and a formation on the adjacent side of said winding leg located opposite said third projection at one position -of said winding leg where it is substantially coextensive with said yoke member, and when said winding leg is turned end-for-end and again positioned to be substantially coextensive with said yoke member said formation will be offset :from all of said projections, said yoke member having a yfourth 4lateral projection at one end `which extends across the adjacent end of said winding leg but is spaced therefrom to form another gap, and said formation lbeing of greater extent than the width of said third projecton so that the length of said other gap may be adjusted by longitudinal movement of said winding leg without affecting the iirsomentioned gap.

4. A core construction comprising, an elongated winding leg, a yoke member at one side of said winding leg, and having a plurality of lateral projections thereon extending toward said lwinding leg, two of said projections eng-aging the adjacent side of said winding leg, a gap between a third of said projections and .the adjacent side of said winding leg `formed by a recess in said adjacent side located opposite said third projection at one position of said winding leg Where it is substantial-ly coextensive with sai-d yoke member, and when said winding leg is turned endfor-end and again positioned to be substantially coextensive with said yoke member said recess will be oifset from all `of said projections, another recess in said adjacent side edge of said winding leg located opposite said third projection at the last mentioned position of said winding leg and being of different depth than the first recess so that the gap may be varied by adjusting said winding leg to a different position relative to said yoke member.

5. A core construction comprising, an elongated winding leg, a yoke member at one side of said winding leg and having a plurality of lateral projections thereon eX- tending toward said Winding leg, two of said projections engaging the adjacent side of said winding leg, a gap between a third of said projections and a formation on :the adjacent side of said Winding leg located opposite said third projection a-t one position of said winding leg Where it is substantially eoextensive with said yoke member, and when said Winding leg is turned endforend and again positioned to be substantially coextensive with said yoke member said formation will be offset `from all of said projections, another formation on said adjacent side edge of said winding leg located opposite said third projection at the last mentioned position of said winding leg and `being of different lateral extent than the `first mentioned formation so that the gap may be Varied by adjusting said Winding leg to a different position relative to said yoke member.

6. A core construction comprising, an elongated winding leg, a lJ-shaped yoke member receiving said winding leg, the legs of said yoke member having spaced opposed f lateral projections thereon extending toward said Winding leg, at least two of said projections on each leg of the yoke member engaging the adjacent side edges of the winding leg and a third projection being spaced from formations on said winding leg to form a leakage gap, the outer end ot said Winding leg substantially co-terminating with the outer ends of the legs of said yoke member, the inner end of said winding leg being spaced from the bight portion ot said yoke member' to form another gap which is adjustable by relative longitudinal movement of said Windin leg, and said formations located so that when said Winding leg is turned end-for-end they will be odset from all of said projections.

7. A core construction comprising, an elongated winding leg, a shaped yoke member receiving said Winding leg, the legs ol? said yoke member having spaced op posed lateral projections thereon extending toward said winding leg, at least two ol said projections on each leg ot' the yoke member engaging the adjacent side edges of the winding leg and a third projection being spaced from formations 0n said winding leg to form a leakage gap, the outer end of said winding leg substantially co-terminating with. the outer ends of the legs of said yoke member, the inner end of said winding leg being spaced from the bight portion of said yoke member to form another gap which is adjustable by relative longitudinal movement of said winding leg, other formations at opposite sides of said winding leg but of different lateral extent than the first-mentioned formations and located so that when said winding leg is turned end-for-end said other formations will be located opposite said third projections to form leakage gaps.

8. A core construction comprising, a plurality of laminations of magnetic material, each of said laminations comprising an elongated winding leg, a yoke member at one side of said winding leg and having a plurality oi lateral projections thereon extending toward said Winding leg, two of said projections engaging the adjacent side of said winding leg, a gap between a third ot said projcctions and the adjacent side of said Winding leg formed by a recess in said adjacent side located opposite said third projection at one position of said winding leg where it is substantially coextensive with said yoke member, and when said Winding leg is turned end-fonemi and again positioned to be substantially coextensive with said yoke member said recess will be offset from all of said pro-- jections, another recess in the adjacent side edge of said winding leg located opposite said third projection at the last mentioned position of said winding leg and being of different depth than the lirst recess so that the gap may be varied by adjusting said winding leg to such dierent positions relative to said yoke member, and certain ot the laminations having the winding leg thereof positioned in endforend relation relative to the position of the winding leg in the other laminations.

References Cited in the tile of this patent UNITED STATES PATENTS 

